The present invention relates to a rotatable tool having a tool body and a replaceable cutting part at the chip removing free end of the tool body. The tool part has helicoidal or straight chip channels, and the cutting part has a cutting edge for chip removing machining. The tool part and the cutting part are interconnected by means of a dovetail coupling which comprises a male part and a female part. The invention also relates to the cutting part per se and to a method of replacing a cutting part. The tool can especially be a drill or a milling cutter.
A twist drill having a replaceable cutting part is previously known from German Document PS-367 010, the cutting part being connected to one of the ends of a drill shank by means of a dovetail coupling. The connection between the cutting part and the shank is entirely based on frictional forces between cooperating surfaces of said parts, and therefore there should be an obvious risk that the cutting part may be dislodged from the correct position thereof during handling of the drill.
A drill having a replaceable cutting part is previously known from U.S. Pat. No. 5,904,455. The cutting part is fixed in a recess in the front end of the drill by a clamping action of the sides of the recess abutting against the cutting part. This clamping action may be provided by inherent elasticity of the material forming the recess (or alternatively the clamping action may be enhanced by applying an axial force to the cutting part), by a suitable design of the bottom of the recess and the portion of the cutting part abutting thereagainst, a compressing force being generated on the cutting insert by the sides of the recess.
Aims and Features of the Invention
A primary aim of the present invention is to provide a tool of the kind defined above where the fixation of the replaceable cutting part takes place in an exceptionally simple but yet reliable manner.
Yet another aim of the present invention is that the cutting part, i.e. the article which is consumed, should be design-wise exceptionally simple.
An additional aim of the present invention is that when assembling the cutting part on the tool part, it should in practice be impossible to assemble the cutting part in the wrong way and that the cutting part in principle automatically takes up a correct position in relation to the tool part.
At least the primary aim of the present invention is realized by a tool which comprises a rotatable tool body and a replaceable cutting tip for chip removing machining. The tool body defines a longitudinal axis of rotation and includes a forward free end which has a first dovetail coupling part formed thereon. The cutting tip includes a front cutting end and a rear mounting end. The mounting end includes a second dovetail coupling part joined to the first dovetail coupling part in tightly clamped relationship therewith. The cutting tip is removable from the tool body by sliding the second dovetail clamping part out of engagement with the first dovetail clamping part in a direction laterally of the axis of rotation. One of the dovetail coupling parts includes a laterally facing stop surface against which the other dovetail coupling part abuts, to limit the extent of insertion of the cutting tip onto the tool body.
The invention also pertains to a cutting tip for chip removing machining. The tip is formed of a hard material (such as ceramics or cemented carbide for example) and defines a longitudinal axis of rotation. The tip includes a front cutting end and a rear mounting end. The rear mounting end includes a female dovetail coupling part formed thereon which extends laterally of the axis.
The invention also pertains to a method of replacing a spent cutting tip with an identical replacement cutting tip. The method includes the steps of:
A) sliding the spent cutting tip out of the first dovetail coupling part in a direction laterally of the axis; and
B) sliding the second dovetail coupling part of the replacement cutting tip into engagement with the first dovetail cutting part in a direction laterally of the axis until laterally facing surfaces of the first and second dovetail coupling parts abut one another.